generally constructed by the males in the Fire-Weavers (Pyromelæna), and in the Yellow and Black African Weavers (Hyphantornis); by the females in the Whydahs (Vidua and allies); by both sexes in Ploceus, although the female only comes in at the finish to assist the male in forming the cup for the reception of the eggs.
It is certainly a most interesting sight to notice how a Hyphantornis, with beak and claw, commences his snail-shell-shaped nest, attaching it to the wirework over the top of an aviary. He is so quick in passing an end of grass through the wire, holding it with one claw, then with his beak pulling it back through the next mesh. But the true Weavers are marvellous; they are born architects, and delight in their work as many an old lady does in knitting.
It is instructive to watch Waxbills (Estrilda and allies) at work—the female inside the nest, the male outside—alternately passing the end of a grass-stem backwards and forwards, until a strongly-laced, but semitransparent, globe is formed, with entrance-hole in front (but not invariably with depressed entrance-shaft leading to it). And, speaking of this netting instinct in Weavers, reminds me that among the cup-builders there is a group of very clever Weavers (Spermophila), whose nests are suspended between twigs, and formed of fine tough fibre. I supplied my birds with fine willow-fibre, and the delicate lacelike nests, of which unfortunately I did not preserve a specimen, were beautiful little works of art.
How does a bird learn to build the nest which is characteristic of its species, its genus, or its family? Charles Dixon asserted that the young bird remembered and copied the nest in which it was reared—that its gifts were not instinctive. On the other hand, I assert that a bird, by seeing the inside of its parents' nest, could not understand how it was formed inside, much less outside; and that experiment proves conclusively that it does not necessarily form its nest on the pattern of that in which it was reared.
Charles Dixon speaks of a Chaffinch introduced into New Zealand which built a long tapering nest, somewhat resembling that of one of the native birds of that country, as evidence of the truth of his statement. Seebohm, however, in
